added new methods to get information about already registered types

SmallInjector/Container.cs

@@ -11,22 +11,30 @@ namespace SmallInjector
         private readonly Dictionary<Type, RegisteredType> _container = new Dictionary<Type, RegisteredType>();
 
         /// <inheritdoc/>
-        public void RegisterType<TService, TInterface>(bool isSingleton, TService instance = default) where TService : TInterface
+        public void RegisterType<TService, TInterface>(bool isSingleton, TService instance = default)
+            where TService : TInterface
         {
             _container.Add(typeof(TInterface), new RegisteredType(typeof(TService), isSingleton, null));
         }
 
         /// <inheritdoc/>
-        public void RegisterType<TService>(bool isSingleton, TService instance = default) => RegisterType<TService, TService>(isSingleton, instance);
+        public void RegisterType<TService>(bool isSingleton, TService instance = default) =>
+            RegisterType<TService, TService>(isSingleton, instance);
 
         /// <inheritdoc/>
         public TService Resolve<TService>() => (TService) Resolve(typeof(TService));
 
+        /// <inheritdoc />
+        public bool IsRegistered<TService>() => IsRegistered(typeof(TService));
+
+        /// <inheritdoc />
+        public bool IsRegistered(Type serviceType) => _container.ContainsKey(serviceType);
+
         /// <inheritdoc/>
         public object Resolve(Type serviceInterface)
         {
             if (!_container.TryGetValue(serviceInterface, out var registeredType))
-                throw new Exception("Can't resolve dependency " + serviceInterface);
+                throw new Exception(@"Dependency {serviceInterface} is not registered");
 
             if (registeredType.IsSingleton && registeredType.Instance != null)
                 return registeredType.Instance;
@@ -37,22 +45,23 @@ namespace SmallInjector
             {
                 constructorParameters[i] = Resolve(parameters[i].ParameterType);
             }
+
             var instance = constructor.Invoke(constructorParameters);
             return registeredType.IsSingleton ? (registeredType.Instance = instance) : instance;
         }
 
         private class RegisteredType
         {
+            public bool IsSingleton { get; }
+            public Type ServiceType { get; }
+            public object Instance { get; set; }
+
             public RegisteredType(Type serviceType, bool isSingleton, object instance)
             {
                 ServiceType = serviceType;
                 IsSingleton = isSingleton;
                 Instance = instance;
             }
-
-            public readonly bool IsSingleton;
-            public readonly Type ServiceType;
-            public object Instance { get; set; }
         }
     }
 }

SmallInjector/IContainer.cs

@@ -30,5 +30,15 @@ namespace SmallInjector
         /// Resolve service of specified type.
         /// </summary>
         TService Resolve<TService>();
+
+        /// <summary>
+        /// Returns true, if the service is registered. False otherwise.
+        /// </summary>
+        bool IsRegistered<TService>();
+
+        /// <summary>
+        /// Returns true, if the service is registered. False otherwise.
+        /// </summary>
+        bool IsRegistered(Type serviceType);
     }
 }